Many, if not a majority, of commercial buildings are constructed with flat roofs with raised parapet walls around the building perimeter and at other locations within the footprint of the roof. Traditionally, the top of the parapet wall has been terminated and sealed with a cut stone, masonry, or precast concrete coping cap set in mortar and/or sealant. Some purposes of the coping cap are to aesthetically accent the top of the wall, and to seal the wall cavity from moisture infiltration and “wind washing”. The coping cap stone is generally slightly wider than the wall so as to create a small (1″-3″) overhang on each face of the wall for additional weather protection.
Traditional coping caps remain desirable for their aesthetic appeal, but due to their high cost and relatively poor performance with respect to weather tightness, stone, masonry, and precast concrete coping caps have been largely replaced by continuous lengths (3 feet to 20 feet long, with 10 feet being most common) of sheet metal coping caps. The sheet metal coping caps are basically “C” shaped profiles of unpainted or prefinished sheet metal. The metal coping cap is sized to slip over the wall section with each flange of the “C” oriented vertically and secured to the inside and/or outside face of the wall. At one or both longitudinal edges, an angled “drip lip” may be formed into the metal coping cap. Some metal coping systems rely on exposed fasteners for securement to the wall; some on concealed cleats that the coping is then crimped onto; and others on discontinuous sheet metal “anchor chairs” that provide a springing mechanism which results in no exposed fasteners.
Metal coping systems are most often formed from aluminum or steel sheet metal. However, some coping systems are also formed from sheet copper, stainless steel, or zinc material. Very often, aluminum and steel coping systems are painted, and most often, these painted metal coping systems are made from prepainted flat sheet metal stock which has been processed by the “continuous coil coating” method in which very long (2,000 to 20,000 feet long) coils of sheet metal are painted with multiple chemical dipping treatments and coats of specialized roller applied paints preferred by the building products industry. In this way, metal coping systems are widely and economically available in many colors with high performance paint systems that are warrantied for up to 30 years of service.
The Difficulty with Prefinished Metal Coping Systems
While prefinished metal coping systems offer significant performance, longevity, and aesthetic appeal at a moderate price, the systems currently lack an equally exceptional method of providing coping system continuity wherein two or more walls join, such as at a building corner. At any transition, for instance an outside corner of the building, a metal coping system is required to be formed in an acute “L” shape in plane view, while maintaining a “C” shaped cross sectional profile. In all methods of accomplishing this, a section of continuous metal coping can be cut and arranged in such a way as to result in a sheet metal joint at an angle with respect to each of the walls (for a 90° building corner, this seam would be oriented at a 45° angle, from the corner of the outside face of the wall corner to the inside face of the wall corner). At this sheet metal joint, one side of the coping cap is secured to the other side of the coping cap to form a single secured and sealed unit to cap the wall at each wall transition. Currently, there are a number of methods of joining the sheet metal together at the miter joint, each with an aspect rendering the miter unit inferior to the continuous lengths of metal coping away from the wall corner or transition.
First, the miter joint can be secured with mechanical fasteners (rivets, screws, or bolts) and sealed with caulk. This method can be accomplished with both bare and prefinished metals of all types, but results in a coping cap with visible, obtrusive fastener penetrations and possible sealant migration. Furthermore, for prefinished metals, the paint used for the fasteners will fade at a different rate than the coil-coated prefinished sheet metal, thus rendering the fasteners, over time, lighter or darker than the adjacent sheet metal.
Second, some metals, such as aluminum and stainless steel, can be welded; others, such as copper and zinc, can be soldered. Although costly and requiring skilled craftsmen, the metal joint can be secured and sealed by fusing the metal together at the joint by one of these methods. Galvanized or Galvalume® steel cannot be fused by these methods without dramatically increasing the risk of rust corrosion at the joint. In the case of bare metals fused together, the sheet metal joint will be discolored, whether by dark marks from the heat of welding, from the flux solution applied to the metal surface before fusing, or by silver colored solder filler metal on natural copper or zinc sheet. In the case of bare metals, this aesthetic anomaly is endured, as no better a solution currently exists. In the case of prefinished metals that are fused together, the paint coatings must be removed prior to fusing the materials together. After being fused together, either the joint area or the entire miter section must be repainted.
With current technology, even using a paint system with the same resin and pigment types as used by the continuous coil coating process, the post-fusing painting of these mitered components will result in a finish that may be slightly different than the adjacent prefinished metal coping sections, and will certainly fade at a different rate over time. So, even welded and fully post-painted miter and transition sections will appear different in coloration over a short period of time when compared to adjacent straight lengths of prefinished metal coping caps.
It is currently possible to fuse all miter and transitional sections together and post-paint all coping caps and transitions, as well as all straight lengths of coping cap to insure that the entire coping system weathers, fades, and discolors at the same uniform rate. While this eliminates several objections of the above mentioned methods, this is a generally cost prohibitive and time consuming process. Furthermore, the post-applied paint systems use on average 500% more paint material, with more VOC release, and an overall lower level of performance when compared to the continuous coil coating method used for prefinished sheet metal.
In view of the current state of the prior art, there remains a need for a coping cap that overcomes the deficiencies of prior art coping caps.